Fuel proportioning device



APl'il 3, 1945. J. w. coLvlN ETAL 2,372,766

FUEL PROPORTIONING DEVICE Filed April 2l, 1942 L-llul ATTORN EY.

Patented Apr. 3, 1945 lUNVrl-:D STATES PATENT oFFlce FUEL PROPORTIONING DEVICE James W. Colvin and Frederick V. H. Judd, West Hartford, Conn., assignors to United Aircraft Corporation, East Hartford, Conn., a corporation of Delaware Application April 21, 1942, Serial No. 439,879

4 Claims.

This invention relates to improvements inl A further object resides in a charge forming apparatus of the character indicated which is automatically compensated for variations in air density and will accurately measure the new of intake air in terms of weight or mass of intake air flowing per unit of time.

A still further object resides in theprovision of an improved charge forming apparatus of tzc character indicated which does not require any venturi or other restriction in the air intake system of the engine in order to `measure the quan- I tity of intake air flowing to the engine and, by

thus facilitating the flow of intake air, increases the eiciency of the engine supercharger and also increases the efficiency of the engine, particularly at high altitudes.

A still further object of the, invention is to automatically compensatefor variations in the temperature of the air forming part of the charge.

An additional object resides in the provision of an improved charge forming device of the character indicated which is electrically actuated and is`light in weight and simple in construction and operation.

Other objects and advantages will be pointed out hereinafter or will become apparent as the description proceeds.

ln the accompanying drawing, in which like reference numerals are used to designate similar parts throughout, there is illustrated a suitable mechanical embodiment for the purpose of disclosing the invention. The drawing, however, is forthe purpose of illustration only and is not to be taken as limiting or restricting the invention as it will be apparent to those skilled in the art that various changes in the illustrated embodiment may be resorted to without in any way exceeding the scope of the invention.

In the drawing, the single ligure is a diagrammatic illustration of a fragmentary portion of an internal-combustion engine, such as is conventionally employed for the propulsion of aircraft, showing the application thereto of a charge forming apparatus constructed according to the invention.

Referring to the drawing in detail, the engine, generally indicated at I0, may have a plurality of cylinders, one of which is indicated at I2, a power shaft i4 fordriving a propulsive device such as an aeronautical propeller, a blower section or supercharger i6 and a fuel pump i8. The

engine may be enclosed in a conventional streamlined cowl 20 provided with an opening or air scoop 22 from which an intake air duct 24 leads to the inlet 26 of the supercharger I6. From the supercharger, intake pipes, one of which is indi cated at 28, lead to the intake ports of the various engine cylinders and fuel lines 3U lead from .the pump I8 to the various cylinders to inject metered quantities of fuel into the cylinders at properly timed intervals. The fuel pump i8 illustrated is of a type well known to the art and frequently referred to as Bosch type fuel-injection pump and is driven from the engine by a suitable drive mechanism not illustrated. The quantity of fuel injected by the pump is controlled by rotation of a regulating shaft 32 which varies the stroke or displacement of the pump plungers in a manner well known to the art.

While a particular type of fuel injection pump has been illustrated for the purpose of disclosing the invention, it is to be understood that the invention is not in any Way limited to this particular type of pump or to a fuel injection engine but that any other type of fuel feeding apparatus may be used providing it is subject to control to accurately meter the quantity of fuel supplied to the engine.

Within the intake air duct 24 between the entrance opening 22 and the supercharger inlet 26 there is a throttle 34 which may be either manually or automatically operated and in the arrangement shown, between this throttle and the supercharger air intake there is a wire resistance grid or filament 36 extending across the interior of the air intake duct. however, may be located at any point in the induction system in which it is subject to the total air flow through the system.

While the drawing shows an engine having a supercharger I6, it is to be understood that the invention is in no way limited to such an engine but that the improved charge forming apparatus may be applied with equal facility to an un-supercharged engine in which case the grid or filament 36 would be disposed in the intake air duct somewhere in the induction system.

The grid or filament 36 constitutes one element This grid or lament,`

high frequency alternating current generator Il. A

The alternating current may pass through the portion of the bridge circuit including the conduit 46, the condenser 48, the temperature responsive resistance 50, the condenser 52, the resistance l and the conduit 54 and may also ow through the portion of the bridge circuit including the conduit 4B, the condenser 56. the resistance 3, the condenser 58, the resistance 3B, the adjustable rheostat 6U and the conduit 5I. In accordance with the operative principles of the Wheatstone" bridge, the ratio of current owing through the two parts of the bridge will be controlled by the resistance encountered in each bridge portion. The rst described bridgeportion is connected through a conduit e2 with one terminal 5B of a sensitive alternating current ammeter, generally indicated at 65, and the other portion of the bridge is connected through the conduit t8 with the opposite terminal 61 so that the current flowing through the ammeter is dependent upon the diierence in potential between the two portions the Wheatstone bridge. This bridge is so arranged that it has a normal or initially adjusted unbalance providing a potential which rotates the armature 1i] of the ammeterv against the force of the coil spring 12 to a position such that the pointer 14 is substantially mid-way between the contact point 16 and 16. If now the potential between the two portions of the Wheatstone bridge increases thepolnter 14 will be moved into contact with the point 1S and il the potential decreases the pointer will' be moved by the spring 12 into contact with the point 16 for a purpose which will presently appear.

The above-mentioned difference in potential between the two sides of the Wheatstone bridge is due to the unbalance caused by diierences in the resistance in the -circuit constituting these two bridge portions. The resistances 38 and 40 are substantially xed or constant and 'may' be different from each other by an amount sufcient Y to produce the normal or initially adjusted unbalance in the bridge circuit resistances described above. Departures from this normal unbalance are caused by variations in the resistance of the resistance elements 38 and 50. These elements may be substantially equal when both are at the same temperature but are so arranged that their resistance variesv rapidly with changes in temperature. An increase in temperature increases the resistance of these elements 36 and vEl! and correspondingly any decrease in temperature reduces their resistance., The resistance grid or filament 36 is heated from a substantially .con-

; stant source of direct current, such as the battery '80, through a circuit includingthe choke coil 82,v the resistance 36 and the variable resistf ance l2. Thisheating circuit for the filament I6 is separated from and is independent of the bridge circuit. As illustrated, this heating circuit is D. C. while the bridge circuit is A. C. Also by o! a form of Wheatstone bridge including the additional resistances 38, 60, 40 and. The

mometer, measuring temperature variations of the intakeair, as well as a ow meter measuring the quantity of intake air flowing past it per unit of time. As the fuel is to be metered by pump VIl in proportion to the quantity of intake air it becomes necessary to compensate the resistance elements for temperature variation and this is done by utilizing the resistance element ill in the other portion of the bridge circuit as a compensating thermometer. This element 5l! is so mounted that it is constantly exposed to temperature variations of the atmosphere but is not" subjected to an appreciable air velocity so that it responds directly to temperature variations and compensates the unbalance between the two portions of the bridge circuit for variations in l idling and full power operation. If desired this rheostat may be ,operatively connected with the control for the throttle 3L in order to render the economizer action automatic upon operation of the throttle to produce theparticular operating condition. l

With the resistance element 3B thus heated by .a predetermined amount and compensated by resistance for variations in the air temperature,

and with a quantity o f heat removed from this element 3B proportional to the weight of air owing past it per unit of time, the change thus caused in the potential between the two portions t of the bridge circuit by the variations in the resistance of the resistance element 3S induced by the abstraction of heat'from this element by theintake air will be proportional to the intake air flow.

The arm 14 of the micro-ammeter 66 is con. nected at its ce ter to a source of current, such as the battery I, while the terminal points 16 and 18 are connected to a reversible electric motor 86 in such a manner as to cause the motor to rotate in one direction when the arm 1l is in contact with the terminal point 16 and in the opposite direction when the arm 14 is in contact with the terminal point 18. The motor is drivingly connected with the pump stroke adjusting shaft 32 to change the cyclic capacity of the pump under the control of the micro-ammeter 66 which is in turn controlled .by the unbalance in the bridge circuit caused by air ilow induced variations in the resistance of the resistance element 36. The shaft of the motor 8B drives a threaded shaft 08 upon which is threaded a nut el slidable in a cross head 92 carried by the motor support 94 and carrying a movable contact 96 which engages the variable resistance 42. This contact is connected through the conduits 98 and N0 into the heating circuit of the resistance element 88 to control the amount of current fed to the resistance element 36 from the battery 8l. By means of this arrangement including the variable resistance. and movable contact 98 the heating Aof the elemeift as is mami-.ames at an times pro-- portional to the quantity of intake air ilowingv past the element to maintain a constant relation-A ship between the quantity of intake air and the resistance nf the resistance element. Whenthe as'ravee motor 8,6 has brought the movable contact 88 to the proper setting tu adjust the flow of heating current through the resistance element 36 for the particular quantity of intake air flowing past this element the bridge circuit will again be balanced, that is, the potential diiference between the two portions of the circuit will return to the value which returns the microammeter arm 14 to its position between the points and 1I and the engine will then continue in operation with the new pump setting until the quantity of intake air is again varied, which variation will cause a resetting of the pump regulator in the manner indicated above. When the mass flow rate of intake airincreases, the temperature of nlament 36 decreases which unbalances the bridge circuit. More heating current is then required to balance the bridge circuit and restore the temperature of the filament 3G to normal. To accomplish this the screw 88 when rotated with shaft 32 to increase the fuel delivered by pump II moves the contact 98to reduce the resistance 42 in the heating circuit. Similarly when the mass ow rate of intake air decreases, the temperature fila'- ment 36 increases and unbalances the bridge circuit in the opposite direction and moves the contact 96 in a direction to increase the resistance 42 in the heating circuit.

While, in the apparatus shown, the arrangement utilizes a relatively large direct current for heating the resistance element ll and a relatively small high frequence alternatingv current for ,the bridge and ammeter circuits, it would be entirely feasible by slightly revising the circuit .to

retain the separation of the currents to reverse these currents, using a direct current for the closing the invention, it is to be understood that the invention is not limited to the particular embodiment so illustrated and described but that such changes in the size, shape and arrangement of the parts may .be resorted to as come within the scope of the sub-joined claims.

Having now 4described the invention sov that others skilled in the art may clearly understand the same, what it is desired to secure by Letters Patent is as follows: Y

1. A fuel controlling means for an internal combustion engine comprising, an air intake duct, an adjustablel fuel feeding device, la resistance element in said air duct, means to heat said element, said means comprising an electric circuit including said element, electrically actuated means operatively connected .between said resistance element and said fuel feeding device for "ment, and means to vary the heat supplied to Asaid element proportioned to the mass flow of air through said intake duct for different adjustments of said fuel feeding device. f

2. A fuel controlling means for an internal combustion engine comprising, an air intake duct. an adjustable fuel feeding device, electrical apparatus for adjusting said fuel feeding device in accordance with variations in the mass flow rate of air through said air intake duct, said electrical apparatus comprising a resistance element disposed in said air intake having a predetermined variation in electrical resistance with variations in temperature, an electric circuit including said element for supplying heating current directly to said resistance element at a predetermined variable rate proportional to the mass flowof air,

through said intake duct, and means controlled by variations in resistance of said resistance element .to regulate said fuel feeding device.

3. A fuel controlling means for an internall combustion engine comprising in combination, an air intake duct, an adjustable fuel feeding device. and electrical apparatus for adjusting said fuel feeding device in accordance with variations-in the mass flow rate of air through said air intake duct, said electrical apparatus comprising, a resistance element disposed in said air intake duct and having a predetermined variation in electrical resistance with variation in temperature,

means for supplying heating current to said re- A ilow rate of air in said intake duct, and means to vary the heat supplied to said resistance element proportioned to the mass flow of air through said intake duct as said fuel feeding device is adjusted. A

4. A fuel controlling means for an internalcombustion engine comprising, an electrical resistance element positioned in a gas stream, a heating circuit directly connected to said element, a Wheatstone bridge circuit electrically connected with said element, means for energizing one of said circuits with direct current, means for energizing the other circuit with alternating current, a current measuring element in said bridge. circuit and having an element movable in vresponse to current variations in the two sides of said bridge, a fuel metering device having a -regulating element operatively connected with the pump, and means controlled by adjustment of said fuel metering device to vary the current in the heating circuit for said element, whereby the heat applied to said element will be proportioned to the mass flow of air through said intake duct.

JAMES W. COLVIN.

FREDERICK V. H. JUDD. 

